Mass spectrometer having an external detector

Abstract

A mass spectrometer system is disclosed. The mass spectrometer includes a vacuum chamber defining an enclosed evacuated space and an ion trap disposed in the enclosed space. The ion trap is configured to trap an ionized sample. The mass spectrometer further includes an ion detector coupled to the chamber at a location external to the chamber such that sample ions may exit the evacuated space and into the externally-coupled detector without loss of vacuum pressure.

What is claimed is: 
     
       1. A mass spectrometer system, comprising:
 a vacuum chamber defining an enclosed evacuated space; 
 an ion trap disposed in the enclosed space, the ion trap being configured to trap an ionized sample; and 
 an ion detector coupled to the chamber at a location external to the chamber, such that sample ions may exit the evacuated space and into the externally-coupled detector without loss of vacuum pressure. 
 
     
     
       2. The mass spectrometer system of  claim 1 , wherein the chamber includes an aperture configured to direct ions ejected from the ion trap to the detector. 
     
     
       3. The mass spectrometer system of  claim 1 , further including a pump to maintain the chamber under vacuum, wherein the externally-coupled detector is housed in a portion of the mass spectrometer that is not under vacuum. 
     
     
       4. The mass spectrometer system of  claim 1 , wherein the ion detector includes an internal detector tube under vacuum. 
     
     
       5. The mass spectrometer system of  claim 4 , wherein the tube includes an input end and an output end, wherein the input end is configured to engage a wall of the chamber to provide a pressure barrier so as to maintain the chamber and an interior of the tube under vacuum. 
     
     
       6. The mass spectrometer system of  claim 5 , wherein the output end is sealed from the ambient air. 
     
     
       7. The mass spectrometer system of  claim 1 , wherein the chamber has a volume to accommodate only an electron source and the ion trap. 
     
     
       8. A mass spectrometer system, comprising:
 a chamber configured to be maintained under vacuum, the chamber including:
 an ion trap configured to capture ions generated when a sample is ionized by electrons emitted from an electron source; and 
 
 an ion detector configured to detect ions ejected from the ion trap, the ion detector including a tube configured to be maintained under vacuum, the tube being coupled to a wall of the chamber at a location external to the chamber. 
 
     
     
       9. The mass spectrometer system of  claim 8 , wherein the wall of the chamber defines a recess. 
     
     
       10. The mass spectrometer system of  claim 9 , wherein the tube includes an input end, and wherein the input end is configured to be received in the recess to couple the ion detector to the chamber. 
     
     
       11. The mass spectrometer system of  claim 10 , further including an o-ring disposed between the input end and the wall in the recess, wherein the o-ring is configured to provide a sealing interface between the input end and the recess. 
     
     
       12. The mass spectrometer system of  claim 11 , wherein the recess includes a groove to receive the o-ring. 
     
     
       13. The mass spectrometer system of  claim 10 , further including a fastener to exert pressure onto the tube to press the input end into the recess. 
     
     
       14. The mass spectrometer system of  claim 10 , wherein the input end is sized to be press-fit into the recess. 
     
     
       15. The mass spectrometer system of  claim 8 , wherein the tube includes a fastening assembly configured to position the detector relative to the wall so that an input end of the tube is flush against an outer surface of the wall. 
     
     
       16. A mass spectrometer system, comprising:
 a chamber defining an enclosed space configured to be maintained under vacuum, the chamber including:
 an electron source configured to emit ions; 
 an ion trap including:
 a ring electrode; and 
 first and second end cap electrodes which are arranged on opposite sides of the ring electrode, wherein the first end cap electrode includes a first aperture through which electrons emitted by an electron source enter the ion trap, and the second end cap electrode includes a second aperture through which ions are discharged from the ion trap; and 
 
 
 an ion detector configured to detect an amount of ions ejected from the ion trap, the ion detector being coupled to the chamber at a location external to the chamber. 
 
     
     
       17. The mass spectrometer system of  claim 16 , further including an amplifier coupled to the ion detector at a location external to the chamber. 
     
     
       18. The mass spectrometer system of  claim 16 , wherein the ion detector is a discrete dynode electron multiplier. 
     
     
       19. The mass spectrometer system of  claim 16 , wherein the ion detector is a channel electron multiplier (CEM). 
     
     
       20. The mass spectrometer system of  claim 16 , wherein the ion detector includes a vacuum tube having an input end and an output end, wherein the input end sealingly engages a wall of the chamber.